Modified Three-Dimensional Digital Technique in the Measurement of the Rotation Alignment of the Distal Femur

Li Guangxu; Zhou Rong; Huang Wei

Abstract：Objective To evaluate the accuracy of a modified technique of measurement of the rotation alignment of the distal femur with the using of three dimensional (3D)construction .Methods Twenty two volunteers in Chongqing were enrolled in this research ,including 11 men and 11 women ,aging from 22 to 50 years old ,average age is (32 .55 ± 18 .33)years .Bilateral lower limb CT scan was done for each volunteer ,and data were collected for following research . Firstly ,the femoral mechanical axis was obtained ,and two methods were used to measure the angles .One method is CT perpendicular to the femur mechanical axis ,the other method is the modified 3D CT determination .The measurement of the posterior condylar angle(PCA) ,the angle between CEA(clinical transepicondylar axis) and SEA(surgical transepic-condylar axis) ,the condyle twist Angle(CTA) were done.Results Posterior condylar angle was (3 .24 ± 1 .18)° in tomography determination group ,and (3 .26 ± 1 .23)°in 3D measurement group ,(P＞0 .05) ;condyle torsion Angle value was (7 .11 ± 1 .06)°in tomography determination group ,and (7 .15 ± 1 .13)°in 3D measurement group (P＞0 .05) ;surgi-cal transepiccondylar axis and clinically transepicondylar axis Angle value was (3 .85 ± 0 .43)°in tomography determina-tion group ,and (3 .92 ± 0 .41)°in 3D measurement group (P＞0 .05).There was no significant difference between the two methods in the same rotation angle .There was no significant difference between left and right angles ,and no signifi-cant difference between male and female angles too .Conclusion Both tomography determination and 3D measurement can obtain accurate parameters of the rotation angle of the distal femur .